Custom Arrow Tips

[behackl]

List of Changes

• Refactor ArrowTip in geometry.py to be a (actually quite concrete) abstract base class so that different arrow tip shapes can be implemented by inheriting from it.
• Add ArrowTriangleTip (the current default tip), and two new tips ArrowCircleTip, ArrowSquareTip.
• Add keyword tip_shape to pass the custom shape to the Arrow constructor.

Motivation

This is part of #272.

Explanation for Changes

This PR changes the class hierarchy for arrow tips a little in order to allow the (easy) implementation of custom tips. Details are given in the List of Changes.

Testing Status

As an example, rendering the ArrowTest scene in the Snippet

import numpy as np

from manim import Scene, Arrow, ShowCreation, FadeOut,\
                  ArrowTriangleTip, ArrowSquareTip, ArrowCircleTip


class ArrowTest(Scene):
    def construct(self):
        a11 = Arrow(np.array([-2,3,0]), np.array([2, 3, 0]))
        a12 = Arrow(np.array([-2,2,0]), np.array([2, 2, 0]),
                    tip_shape=ArrowTriangleTip,
                    tip_style={'fill_opacity': 0, 'stroke_width': 3})
        a21 = Arrow(np.array([-2,1,0]), np.array([2, 1, 0]), tip_shape=ArrowSquareTip)
        a22 = Arrow(np.array([-2,0,0]), np.array([2, 0, 0]), tip_shape=ArrowSquareTip,
                    tip_style={'fill_opacity': 0, 'stroke_width': 3})
        a31 = Arrow(np.array([-2,-1,0]), np.array([2, -1, 0]), tip_shape=ArrowCircleTip)
        a32 = Arrow(np.array([-2,-2,0]), np.array([2, -2, 0]), tip_shape=ArrowCircleTip,
                    tip_style={'fill_opacity': 0, 'stroke_width': 3})
        self.play(ShowCreation(a11), ShowCreation(a12), ShowCreation(a21), 
                  ShowCreation(a22), ShowCreation(a31), ShowCreation(a32))
        self.wait(1)
        self.play(*[FadeOut(obj) for obj in self.mobjects])

yields

Acknowledgement

• I have read the Contributing Guidelines

[huguesdevimeux]

Thanks for your contribution !
As this PR is still WIP; I'm marking it as draft.

[leotrs]

WOWOWOW This is beautiful thanks so much! I'll review in a sec, but thank you!

[leotrs]

Great stuff here!

One more suggestion: I think the current way of creating filled/hollow tips is a bit awkward. Why not add a filled class to each? In this way this code

a12 = Arrow(np.array([-2,2,0]), np.array([2, 2, 0]),
                    tip_shape=ArrowTriangleTip,
                    tip_style={'fill_opacity': 0, 'stroke_width': 3})

becomes this

a12 = Arrow(np.array([-2,2,0]), np.array([2, 2, 0]),
                    tip_shape=ArrowTriangleFilledTip)

[behackl]

Thank you for this lightning-fast review! I was just typing that you don't need to stress yourself, as I don't know how soon I can add documentation and tests. 😄

I'll look at your comments a bit later -- thanks again!

[huguesdevimeux]

Speaking of tests, I think we should wait for #335 to be merged before adding new tests, so it will be easier.

[behackl]

One more suggestion: I think the current way of creating filled/hollow tips is a bit awkward. Why not add a filled class to each? In this way this code

a12 = Arrow(np.array([-2,2,0]), np.array([2, 2, 0]),
                    tip_shape=ArrowTriangleTip,
                    tip_style={'fill_opacity': 0, 'stroke_width': 3})

becomes this

a12 = Arrow(np.array([-2,2,0]), np.array([2, 2, 0]),
                    tip_shape=ArrowTriangleFilledTip)

Great idea! It really was rather clunky before. I've added some convenience classes for filled/hollow tips in e8d076c. :-)

[leotrs]

Great great stuff. BTW, it was extremely helpful of you to leave the commit link in each of your comments. Super easy to review!

[behackl]

Great great stuff. BTW, it was extremely helpful of you to leave the commit link in each of your comments. Super easy to review!

Thank you for the kind words and your reviews! The thing with the commit hashes in the comments is what I like most when I have to review stuff, glad you like it as well. 😄

I'll finish this here up by writing some docstrings, then the draft status of the PR can be removed again. As @huguesdevimeux suggested above, I'll wait with adding tests until #335 is ready (or take care of that in a follow-up PR). 👍

[leotrs]

Sounds like a plan

[behackl]

Formatting inconsistencies are fixed in e0acdeb.

Changing how tips are added to arrows also slightly changed the visuals of DoubleArrow, which is why the corresponding doctest has to be fixed in 48acf99.
Before:

After:

(Notice that the tips were not equally large before, this is fixed now.)

outdated

[leotrs]

@behackl can you please solve the conflicts and make sure that the tests still pass? We just merged #335 which completely rehauled the test suite

[behackl]

There was no actual conflict, I only needed to merge master locally. And of course, black still fails.

Unfortunately, the tests revealed another inconvenience: due to different architectures, numerics are slightly different between operating systems, which leads to numpy yielding -0.0 in macos and 0.0 otherwise. 🙄

I'll come up with a fix for this, or replace the faulty doctests.

[behackl]

• Fixed doctests via 5b6f3aa
• And I also added a graphical unit test in 9f29fdf -- this was very painless and straightforward, thanks to Refactored tests and added new tests tools for videos-tests. #335 :-)

Ready to be reviewed again!

[leotrs]

lol, I did not know about this hack

[leotrs]

Can we get one more approval here? This is super ready @huguesdevimeux @Aathish04

[Aathish04]

Thank you for the contributions!

[huguesdevimeux]

SGTM !

[leotrs]

🥳